There are two common methods for operating air compressors to obtain a desired output air pressure. In one method, an intermittently operated air compressor is mounted on or is connected to an air tank. Compressed air is supplied from the compressor to the tank and from the tank through a hose to an air consuming tool. A pressure switch cycles the air compressor on and off to limit the compressed air pressure in the tank to a predetermined range. The pressure switch is adjustable to obtain a pressure meeting the requirements of the tool or other appliance operated from the compressed air.
According to another method, an air compressor is continuously operated. The compressor output is applied directly to an air output line which connects to an air consuming tool or appliance, such as a paint spray gun. An air pressure regulator valve is mounted at the compressor for limiting the output pressure in the air line. The valve is adjusted to set the maximum line pressure and bleeds any excess compressor output air to the atmosphere once the set pressure is reached. This method is often used for smaller capacity "oilless" compressors which are designed for continuous operation and for operating tools having limited air volume requirements.
Improvements could be made in the pressure limiting valve used in the latter method. A tool may be connected through a relatively long air line or hose to the compressor. For example, a compressor sitting on the ground may be connected to a spray gun or to a pneumatic nailer being used on the roof of a building. When the air flow through the tool is changed, there will be a change in the pressure drop along the air supply hose connected to the tool. Since the pressure adjusting valve is mounted on the compressor, the operator must walk back to the compressor whenever adjustment of the operating pressure at the tool is needed. Further, when the valve is mounted on the compressor, the valve projects from a side or top of the compressor. There is a risk of damage to the rigidly mounted valve during shipment and use of the compressor.